Herein, spam is defined as the abuse of electronic messaging systems, such as the Internet, to send unsolicited bulk messages indiscriminately. While the most widely recognized form of spam is e-mail spam, the term is applied to similar abuses in other media such as, but not limited to: instant messaging spam, Usenet newsgroup spam, Web search engine spam, spam in blogs, wiki spam, Online classified ads spam, mobile phone messaging spam, Internet forum spam, junk fax transmissions, and file sharing network spam.
Spamming remains economically viable because advertisers have no operating costs beyond the management of their mailing lists, and it is difficult to hold senders accountable for their mass mailings. Because the barrier to entry is so low, spammers are numerous, and the volume of unsolicited mail has become very high. It is estimated that in 2009 the average inbox will sustain 4,403 SPAM hits each year.
Most spam is commercial advertising, often for dubious products, get-rich-quick schemes, or quasi-legal services. As noted above, spam costs the sender very little to send and most of the costs are paid for by the recipient or the carriers rather than by the sender. One particularly nasty variant of e-mail spam is sending spam to mailing lists (public or private e-mail discussion forums.) Because many mailing lists limit activity to their subscribers, spammers will use automated tools to subscribe to as many mailing lists as possible, so that they can grab the lists of addresses, or use the mailing list as a direct target for their attacks. A related, or more general, form of spam is to use computer programs and/or routines to automatically fill in other web-forms and/or make automated web-form submissions.
The costs of spam, such as lost productivity and fraud, are borne largely by the public and by Internet service providers, which have been forced to add extra capacity to cope with the deluge. Of course, the Internet service providers simply pass the cost of the extra capacity along to the end users. Spamming is widely reviled, and has been the subject of legislation in many jurisdictions.
Currently, some “solutions” to the spam problem are being attempted. For instance, one such “solution” is image verification, also referred to as “Captcha”. Captcha is a type of challenge-response test used to ensure that a response, an-e-mail, or a web-form is not computing system generated. Current Captcha systems typically involve a first computing system, such as a server computing system, asking a user to complete a simple test which the first computing system is able to generate and then analyze/grade.
Using currently available Captcha techniques, the generated test typically involves displaying multiple symbols, such as letters and/or numbers. Typically the multiple symbols of the generated Captcha test are displayed in a distorted manner such as distorted text images, and/or in abnormal groupings or with abnormal spacing, and/or angled, and/or crossed by an angled line. In addition, the multiple symbols of the generated Captcha test are often displayed as both capital and lowercases symbols.
Using currently available Captcha techniques the user is then asked to key the distorted multiple symbols of the generated Captcha test into a response data entry field on a display screen. In theory, a computing system, as opposed to a human being, is unable to recognize the distorted multiple symbols of the generated Captcha test. As a result, under the currently available Captcha theory, any user entering a correct solution, i.e., entering the correct sequence and format of the multiple symbols of the generated Captcha test into the data entry field is presumed to be a human being, and not a computing system or other automated device. Thus, currently available Captcha techniques are sometimes described as a reverse Turing test, because they are administered by a machine and targeted to a human, in contrast to the standard Turing test that is typically administered by a human and targeted to a machine.
It is worth noting that in many cases, legitimate human users are also unable to recognize the distorted multiple symbols of the generated Captcha test and it is not uncommon for legitimate users to have to enter a response multiple times. Obviously, this represents a significant burden on legitimate users and the problem will only get worse as display screens and user interface devices continue to get physically smaller and smaller.
Captcha systems have historically proven to be reasonably effective. However, more recently, Spammers have developed software scripts and programs that can copy the exact Captcha images and then extract the correct response. Consequently, Captcha has become less effective as a Spam barrier in recent times. Part of the reason Captcha has become vulnerable to Spammer developed software scripts and programs is the static nature of the Captcha images and the fact that they are currently images of letters and/or numbers, i.e., symbols, that can be captured and mapped to symbol identification databases. In short, the Captcha images require no cognitive/human analysis beyond recognizing a set of static symbols.
As a result of the situation described above, spamming remains economically viable even in the presence of currently available Captcha systems. Consequently, the costs of spam, such as lost productivity and fraud, are still borne largely by the public and by Internet service providers.